Science News surveys the role of accumulating mitochondrial damage and dysfunction in aging and age-related disease: "Today, scientists suspect that millions of people may be suffering from mitochondria gone awry, in more subtle but nonetheless insidious forms. Evidence suggests that malfunctioning mitochondria could explain Alzheimer's disease, Parkinson's, diabetes, cardiovascular disease, obesity, cancer and other consequences of aging. Given the organelle's core function in the body, some think mitochondria might even be the biological epicenter of aging itself: If you live long enough, all your cells might experience a kind of energy crisis. ... I strongly believe that mitochondrial metabolism is the key to aging ... In Mattson's view, and that of other researchers who suspect that people are only as young as their mitochondria, mild amounts of stress force mitochondria to make better use of the glucose available - whether that stress is from calorie restriction or another source. Stress also causes cells to produce proteins that protect the mitochondria from free radical damage. And Mattson points out that other conditions that strain energy production - such as physical and mental activity - also appear to strengthen tissues at the same time."